Field of the Invention
Embodiments disclosed herein relate generally to hydrogen sulfide scavenger blends. In particular, embodiments disclosed herein relate generally to methods of predicting and/optimizing hydrogen sulfide scavenging capacity and reducing scale formation.
Background Art
Hydrocarbons, gases or liquid, are found in geologic formations located beneath the earth's surface. In particular, as obtained from beneath the earth's surface, raw natural gas is a mixture of gaseous hydrocarbons and non-hydrocarbon impurities, and thus, the undesirable impurities, including water, carbon dioxide, and sulfides (e.g., hydrogen sulfide). The presence of hydrogen sulfide or other sulfides is objectionable because such compounds may react with other hydrocarbons or fuel system components, are often highly corrosive and flammable, poisonous in very small concentrations, and emit highly noxious odors. However, sulfides are often present in crude oil and produced oil in addition to the gas phase.
Due to the offensive odor attributed to H2S, H2S-containing gas is often called “sour” gas, whereas treatments to reduce or remove H2S are often referred to as “sweetening.” Substantial amounts of sour natural gas are currently being produced from natural gas wells, oil wells (as associated gas), and from natural gas storage reservoirs that have been infected with H2S-producing bacteria. The presence of H2S in fuel and other gaseous streams has long been of concern for both the users and the producers of such gaseous streams. For example, in the case of natural gas, historically about 25% of the natural gas produced in the United States has been sour, that is, containing greater than about 4 ppm H2S (5.7 mg H2S/m3). In addition to the corrosive and other adverse effects that such impurities have upon equipment and processes with which such gaseous streams interact, noxious emissions are commonly produced from combustion of the natural gas as a result of oxidation of the hydrogen sulfide. The resulting sulfur oxides are a major contributor to air pollution and may have detrimental impact upon humans, animals, and plant life. Increasingly stringent federal and state regulations have accordingly been promulgated in an effort to reduce or eliminate sulfurous emissions, and a concomitant interest exists in efficiently removing from natural gas streams and the like the hydrogen sulfide that comprises a significant precursor of the emissions.
The sweetening or removal of H2S from petroleum or natural gas is only one example of where H2S level reduction must be performed. Other examples of where such technology is applied include the manufactured gas or coke-making industries, where coal gas contains unacceptable levels of H2S due to the distillation of bituminous coal having high levels of sulfur, the manufacture of water gas or synthesis gas where steam is passed over a bed of incandescent coke or coal that may contain sulfur, etc.
Regardless of the source of the liquid or gas stream from H2S is desired to be removed, there have been several mechanisms by which H2S is removed, including selective adsorption via absorbents and/or selective reaction of H2S with a reagent to produce a readily separable product. Such reagents are often termed H2S scavengers whereby the fluid stream is sweetened by the scavenging (removal or reduction) of H2S present in the sour gas (or other contaminated fluid streams). Hydrogen sulfide scavenging agents are most commonly applied through one of the following three methods: (1) batch application of liquid scavenging agents in a sparged tower contactor; (2) batch application of solid scavenging agents in a fixed-bed contactor; or (3) continuous direct injection of liquid scavenging agents. While gas streams must be free (or substantially free) of hydrogen sulfide prior to use, it is also preferable that such contaminants be removed or reduced prior to transport or processing in oil field equipment, pipelines, and refineries due to their corrosivity and flammability. Thus, a growing segment of the natural gas industry uses H2S scavenging processes at remote locations to remove low concentrations of H2S (usually less than about 300 ppm) from sub-quality natural gas.
Conventional H2S scavengers having included amines, aldehydes, alcohols, and reaction products of these materials. Many of such compounds are either too expensive for commercial use or evidence insufficient levels of hydrogen sulfide removal.
Accordingly, there exists a continuing need for developments in hydrogen sulfide removal from fluid streams contaminated with hydrogen sulfide.